Show HN: Nexus-Arc – pay-per-call and job escrow for AI agents on Arc

Hi HN — I built Nexus-Arc. AI agents can call APIs and run multi-step work, but they still cannot open a Stripe account or hold a corporate card. Prepaid credits lock capital; L1 fees make $0.001 calls uneconomic; L2 batch latency breaks tight loops. Nexus-Arc is a dual-rail gateway live on Arc mainnet (chain 5042), where USDC is native gas: 1. Synchronous rail — HTTP 402 / x402. Agent hits an endpoint unsigned, gets a 402 + challenge, signs a Permit2 / EIP-712 voucher, retries with PAYMENT-SIGNATURE. Settlement is in-process, sub-second, pay-per-call. No API keys. 2. Asynchronous rail — ERC-8183 escrow (NexusJobs). Client locks a USDC budget, provider submits a deliverable hash (IPFS/Arweave), evaluator releases payout. State machine: Open → Funded → Submitted → Terminal. Expiry refunds the client. Live screener (expect HTTP 402 on an unpaid GET): https://nexus-arc.pryx.dev/v1/screener https://nexus-arc.pryx.dev/v1/screener Explorer: https://explorer.arc.io https://explorer.arc.io Stack is Bun + Effect TS on Arc. Fees are small (x402 ~0.1% + $0.0005; escrow 75 bps on completion). Happy to answer questions on the 402 self-facilitation path, Permit2 vouchers, or the escrow evaluator. What should I wire next — MCP tools, more paid APIs, or agent identity (ERC-8004)?